Ground water sensitivity to climate variability in the white Bandama basin, Ivory Coast

Introduction Precipitation is one of the major factors in the water balance of a catchment and as such the water cycle is most sensitive to changes in rainfall (Petheram et al. 2002). In sub-humid, semi-arid and arid regions, evapotranspiration is the second largest component of the water balance, and is affected not only by the availability of water but also by any change in other aspects of climate (e.g. temperature) (Russell et al. 2010). Some of the most useful variables for monitoring the water cycle are river flows, ocean water level, rainfall, air and water temperatures, melting of ice cap and groundwater static level (Ouarda et al. 1999; Ardoin-Bardin 2004; Gachon et al. 2007). Analyses of hydrometric and rainfall data in Africa have demonstrated that climate is changing (Ardoin-Bardin 2004; Kouakou et al. 2007; Richard & Parker 2009). This change is characterized by a dry period which began in the 1970s and continues until the present day. A de crease was observed in rainfall intensity (Houndénou and Hernandez 1998; Mowor et al. 2009), number of rainy days (Paturel et al. 1997; Servat et al. 1999), annual rainfall (Mistry & Conway 2003; Schreck & Semazzi 2004; Black 2005; Kebede et al. 2006), and consequently river flows (Kebede et al. 2006; Mc Mahon et al. 2007; Mahé 2009) and lakes levels (Olago et al. 2009). In western Ivory Coast, the impact of climate variability on groundwater resources in the Man area, shows a significant decrease in rainfall and river flow (Savane et al. 2001; Saley 2003). High rainfall variability with an overall rainfall deficit has led to a significant reduction in runoff of about 49% and 27% in the N'Zi and the N'Zo sub-basins of Bandama basin respectively (Goula et al. 2006, Kanohin et al. 2009). On the transborder